A magnetoresistive element has a magnetization free layer whose magnetization direction changes in an external magnetic field; a magnetization pinned layer whose magnetization direction is pinned in the external magnetic field; and a barrier layer that is positioned between the magnetization free layer and the magnetization pinned layer and that exhibits a magnetoresistive effect. The barrier layer is an oxide of an alloy that includes Mg and Al, and the barrier layer includes a crystalline region and a non-crystalline region.